Hi Naysen,
I see what you mean about the slope of your wall presenting problems. Using the dimensions from your link showing the wall block you used, I did a quick sketch of the wall in vertical cross-section with each tier of blocks set back an inch. I've indicated where you might bore a 1" diameter hole through several layers of the wall to insert the rebar or whatever support poles. Hopefully the pdf will attach OK. I think it's pretty self-explanatory (planter soil would be to the left of the sketch).
Here's an example of a 16" drill bit - but you can get them longer (16" might be enough). Be sure and read the review
.
http://www.homedepot.com/p/Bosch-1-i...2167/100209210#
You could very well come up with a better/easier solution (actually draping material over your cages sounds like a good idea ) but this is an alternative for you to consider.
BTW, if your block walls are as unstable as you say, you might want to use some rebar or something to stabilize things a bit before this coming winter in case we get the predicted El Nino.
Anne